User user18921 - Mathematics Stack Exchange

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	3,400 reputation	bio	website		visits	member for	8 months
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166

266

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What was the first bit of mathematics that made you realize that math is beautiful? (For children's book)

may 6 at 4:59 Jori Mäntysalo 31

77

115

votes

28

answers

8

kviews

A challenge by R. P. Feynman: give counter-intuitive theorems that can be translated into everyday language

soft-question big-list examples-counterexamples

aug 6 at 1:40 John 1

41

109

votes

13

answers

4

kviews

Can every proof by contradiction also be shown without contradiction?

logic proof-writing proof-theory

nov 28 at 15:29 ctype.h 599

110

106

votes

35

answers

7

kviews

Fun but serious mathematics books to gift advanced undergraduates.

reference-request soft-question big-list

feb 25 at 22:57 arielf 101

29

80

votes

2

answers

2

kviews

Can we ascertain that there exists an epimorphism $G\rightarrow H$?

abstract-algebra group-theory finite-groups morphism

may 4 at 1:53 user32240 4,856

40

67

votes

5

answers

3

kviews

In (relatively) simple words: What is an inverse limit?

category-theory intuition universal-algebra

mar 29 at 8:55 Pieter Cuijpers 31

21

54

votes

6

answers

2

kviews

Is non-standard analysis worth learning?

analysis soft-question nonstandard-analysis

may 16 '12 at 21:58 Pete L. Clark 44.5k

10

54

votes

2

answers

2

kviews

Does this property characterize a space as Hausdorff?

general-topology

nov 14 '10 at 21:08 Arturo Magidin 158k

32

49

votes

16

answers

8

kviews

If $AB = I$ then $BA = I$

linear-algebra matrices

may 1 at 22:19 mezhang 1,403

51

47

votes

24

answers

10

kviews

Best book ever on Number Theory

number-theory soft-question big-list reference-request

feb 4 at 21:12 Andrew 1,643

14

46

votes

5

answers

1

kviews

Why does mathematical convention deal so ineptly with multisets?

notation terminology math-history multisets

nov 7 at 11:00 Charles Stewart 1,847

26

44

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6

answers

1

kviews

How Do You Actually Do Your Mathematics?

soft-question notation education

mar 5 '11 at 0:24 Billare 993

21

44

votes

1

answer

2

kviews

How do we know an $ \aleph_1 $ exists at all?

set-theory cardinals

may 17 at 11:58 wendy.krieger 305

15

44

votes

6

answers

1

kviews

How far can one get in analysis without leaving $\mathbb{Q}$?

analysis number-theory logic philosophy constructive-mathematics

may 10 at 16:03 Alexander Gruber♦ 15.1k

15

42

votes

12

answers

3

kviews

All natural numbers are equal.

induction fake-proofs

may 8 at 12:01 Lucian Depold 121

9

40

votes

5

answers

2

kviews

In what sense are math axioms true?

logic philosophy axioms

apr 4 '12 at 0:26 jerico 82

41

40

votes

2

answers

3

kviews

Why study Algebraic Geometry?

algebraic-geometry soft-question

jan 24 at 0:49 Javier Álvarez 4,794

18

40

votes

5

answers

1

kviews

Why are groups more important than semigroups?

abstract-algebra group-theory soft-question semigroups big-picture

jan 15 at 17:04 Steven Gamer 135

23

39

votes

5

answers

1

kviews

What are the issues in modern set theory?

reference-request set-theory

mar 7 '11 at 17:22 JDH 18.5k

18

37

votes

5

answers

784

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Why are the solutions of polynomial equations so unconstrained over the quaternions?

polynomials roots quaternions abstract-algebra

may 7 '12 at 6:46 Marc van Leeuwen 23.8k

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36

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19

answers

3

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Mathematical subjects you wish you learned earlier

soft-question learning

feb 13 at 23:19 andyvn22 101

21

32

votes

4

answers

1

kviews

How is $\mathbb{C}$ different than $\mathbb{R}^2$?

complex-analysis

nov 29 '11 at 18:10 Steven Stadnicki 14.2k

15

32

votes

6

answers

1

kviews

Why is compactness in logic called compactness?

general-topology logic terminology compactness

jan 26 at 18:25 Holdsworth88 3,465

14

32

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1

answer

411

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Unexpected approximations which have led to important mathematical discoveries

soft-question math-history big-list experimental-mathematics

1d ago O.L. 4,206

8

31

votes

6

answers

1

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Why don't analysts do category theory?

analysis functional-analysis soft-question category-theory

jan 2 at 23:59 paul garrett 10.5k

13

31

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8

answers

5

kviews

What is the meaning of the third derivative of a function at a point

calculus geometry physics education

mar 28 at 3:36 Brady Trainor 597

7

30

votes

6

answers

908

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Why do we negate the imaginary part when conjugating?

complex-analysis analysis soft-question complex-numbers

mar 28 at 20:56 Joseph 1,906

20

30

votes

8

answers

3

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When to learn category theory?

abstract-algebra category-theory

mar 1 at 10:38 Rasmus 9,458

16

30

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3

answers

2

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Do you prove all theorems whilst studying?

soft-question intuition education self-learning learning

apr 24 at 2:09 Community♦ 1

9

30

votes

10

answers

1

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Why are addition and multiplication commutative, but not exponentiation?

arithmetic tetration hyperoperation

may 14 at 2:36 Gottfried Helms 7,197

user18921

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